I've got a Ruger Mark II Target that had a Weaver rail mounted to it by Clark Custom sometime in the 90s I think. I'm not sure if they did any trigger work to it as well, but it's a pleasure to shoot.
Detonics experimented with a revolver called the Modular 7 shot, it was a Top break and had a similar barrel profile to a ppc, such a gorgeous design, shame it never went to market. My favorite revolver design of all time is from the show “Trigun” the main character “Vash the Stampede” has a Top break revolver. Its built like a PPC but the barrel is on the bottom chamber like a Chiappa Rhino or Mateba Unica